Interpenetrating polymers derived from unsaturated polyesters and isocyanates have already been prepared and described in the Prior Art.
U.S. Pat. No. 4,386,166 describes foams based on modified polyesters obtained from mixing together two reactive components containing foaming agents, one of which consists of a mixture of an unsaturated polyester with a low molecular weight polyol and with catalysts for the formation of urethanes and isocyanurates, while the other component consists of a mixture of a polyisocyanate with a peroxide and a urethane catalyst.
The components of such reactive systems combined with each other, are not susceptible to yield cross-linked (interpenetrated) products possessing adequate characteristics of impact strength nor to be used in the manufacture of products by means of the "lay-up" process.
In U.S. Pat. No. 4,581,384 are described rigid foams with improved dimensional stability, obtained by the combination of two reactive systems, one of which consists of a polyol and a hydroxyl-terminated unsaturated polyester, while the system consists of a poly-isocyanate and a vinyl-monomer capable of cross-linking with the polyester, the stoichiometric ratio NCO/OH in the whole of the two systems being at the most 1.5/1.
Also in this case, the whole of the components of the two reactive systems turns out to be unsuitable for the preparation of manufactured articles with characteristics of high rigidity together with high impact strength, nor for use in the "lay-up" type process.
Thus, the object of the present invention is that of providing cross-linkable polymeric compositions suitable for the manufacture of composite materials and characterized by inherently improved impact strength with respect to the unsaturated polyesters. Moreover, these compositions are characterized by a lesser shrinkage during the cross-linking processes, a lower content in vinyl monomers, in particular styrene, and in other volatile monomer, and, at last, by better self-estinguishing properties though maintaining the other properties of the unsaturated polyesters.
Such compositions, which form one of the objects of the present invention, consist of the following components in admixture with each other, at the indicated by-weight ratios:
A) at least one isocyanate liquid when in admixture with the other components, having a functionality of at least 2 and not greater than 5, but preferably comprised between 2and 4, and a viscosity at 25.degree. C. comprised between 20 and 10000 cPs, but preferably between 40 and 1000 cPs; PA1 B) at least one polyol with a functionality of at least 2 and not greater than 7, but preferably comprised between 2 and 5, having a molecular weight of at least 200 and less than 10,000, but preferably comprised between 300 and 5000, in such a quantity as to ensure a molar ratio (NCO/OH) between the isocyanate groups of component (A) and the hydroxyl groups be comprised between 2 and 8 but preferably between 3 and 7; PA1 C) at least one vinylester or polyester resin, containing ethylenic unsaturations of the vinyl or vinylidenic type, in a 30-80% by weight admixture in a vinyl or divinyl monomer, as defined further below, in such a quantity that (C) represents from 20 to 80% of the sum of weights of (A)+(B)+(C); PA1 D) at least one initiator of radical polymerization by itself stable at temperatures below 70.degree. C., and in quantities comprised between 0.1% and 4% by weight on the sum of weights of (A)+(B)+(C); PA1 E) at least one decomposition promoter of initiator (D) at temperatures below 70.degree. C., consisting of a salt soluble in the mixture of (A), (B) and (C), of a transition metal, preferably Co (II) and Mn(II), in a quantity comprised between 0.001 and 0.5% and preferably between 0.001 and 0.05% by weight, calculated on the metal, on the weight of the sum of (A)+(B)+(C), or consisting of an aromatic amine N,N-dialkylsubstituted in a quantity comprised between 0.05 and 1% by weight; PA1 F) at least one trimerization catalyst for isocyanate (A) in quantities comprised between 0.01 and 1% by weight on the sum of weights of (A), (B) and (C); PA1 G) from 0 to 20%, but preferably from 4 to 10%, by weight on the sum of (A), (B) and (C) of a mineral charge exerting a dehydrating action, such as for instance CaCO.sub.3, zeolite powder or paste, molecular sieves and the like. PA1 n=a number comprised between 0 and 4; PA1 Y and Y', either equal to or different from each other, may be H or --CH.sub.3 or, F, Cl, Br. PA1 m=0, 1, 2 or 3. PA1 a) diphenols of the general formula: ##STR6## R.sub.1, R.sub.1, equal to or different from each other, may be --H, --CH.sub.3 or --C.sub.2 H.sub.5, PA1 n=a number comprised between 1 and 4, extremes included. PA1 B) bisphenol A, PA1 C) novolacs, PA1 C=a group derived from a hydroxylterminating ester of the acrylic, methacrylic acid or similar acids; PA1 I=a group derived from a polyisocyanate of the type described previously, and preferably from methylenediphenyldiisocyanate; PA1 D=a group derived from an organic diol of the precedently described type, and preferably from bisphenol A or from similar compounds; PA1 N=a group deriving from a saturated or unsaturated dicarboxylic acid or from one of its anhydrides: PA1 D and t have the same meaning and values described in the previous formula for vinylester resins; PA1 A=a group derived from acrylic or methacrylic acid or similar acrylic compounds; PA1 M=a group derived from an alkylene oxide such as, for example, ethylene oxide, propylene oxide or epichlorohydrin. PA1 1.a) 0.5-3% b.w. of a peroxy-compound represented by: PA1 b) 0.01-0.15% b.w. of 2-ethylhexanoate of cobalt (II) PA1 c) 0.005-0.05% b.w. of 2-hydroxypropyltrimethylammonium 2-ethylhexanoate; PA1 d) 0.1-0.8% of 2,4,6-tris(dimethylaminomethyl)phenol. PA1 2.a) 0 5-3% b.w. of a peroxy compound as in the above point 1; PA1 b) 0.02-0.2% b.w. of cobalt neodecanoate; PA1 c) 0.05-0.4% b.w. of the product of the above point 1.c); PA1 d) 0.1-0.8% b.w. of the product of the above point 1.d). PA1 3.a) from 0.5 to 3% b.w. of at least one peroxy compound as specified herein above under point 1.a); PA1 b) 0.01-0.2% b.w. of a decomposition promotor consisting of a cobalt salt as defined under the precedent points 1.b) and 2.b); PA1 c) 0.05-0.4% b.w. of the product of the preceding point 1.c); PA1 d) 0.1-0.8% b.w. of the product of the herein preceding point 1.d); PA1 e) 0.1-1% b.w. of a 50% solution in diethyleneglycol of sodium N-(2-hydroxy-5-nonylphenylmethyl-N-methyl-glycinate (trimerization catalyst A). PA1 4.a) from 0.5 to 3% by weight of a peroxy-compound like the one of point 3.a) herein above; PA1 b) from 0.01-0.2% b.w. of decomposition promoter as under point 3.b; PA1 c) from 0.1 to 0.8% b.w. of the product of point 1.d); PA1 d) from 0.1 to 1% b.w. of a mixture of the trimerization catalyst A, as defined under point 3.e), with potassium acetate and ethoxylated cocoamine (trimerization catalyst B).
The isocyanates of point (A) are those comprised in one of the following classes:
(I) Isocyanates of general formula: ##STR1## wherein: ##STR2## R.sub.1 , R.sub.2, either equal to or different from each other, may be H or alkyl containing from 1 to 5 carbon atoms;
(II) Isocyanates of general formula: ##STR3## wherein: Y=H, Cl, Br, F or --CH.sub.3,
Typical isocyanates in this class, with Y=H, are produced by MOBAY Chem. Corp. under the trade name of Mondur MR.
(III) Isocyanates of the general formula: ##STR4##
(IV) Isocyanates of the general formula: ##STR5## wherein: X=H, F, Cl, Br or --CH.sub.3,
and the two --NCO groups are not in position 1,2 with respect to each other, as well as the following isocyanates:
2,6-tolylenediisocyanate PA0 2,4-tolylenediisocyanate PA0 1,4-naphthalenediisocyanate PA0 1,5-naphthalenediisocyanate PA0 1,6-naphthalenediisocyanate PA0 2,6-naphthalenediisocyanate PA0 tris(isocyanatopnenyl)methane PA0 cyclohexanediisocyanate PA0 methylene-bis-(4-cyclohexyldiisocyanate) PA0 MDI (methylenediphenyldiisocyanate) modified with carbodiimide; an isocyanate of this type is known as Isonate 143L, produced by Dow Chemical Corp.; PA0 the quasi-prepolymers obtained by condensation of the isocyanates mentioned so far with the polyols as have been previously defined under paragraph (B).
and blends thereof
The isocyanates of class (II) are the preferred ones.
As polyols usable for the compositions according to this invention, there may be cited, just for exemplifying purposes, those obtained by reaction of the following compounds:
with alkylenoxides such as for instance ethyleneoxide and propyleneoxide, 1,2-buteneoxide, epichlorohydrin, etc., and moreover the derivatives of the condensation of such oxides with low molecular weight polyols, both aliphatic such as ethyleneglycol, propyleneglycol, 1,4-butanediol, glycerol, trimethylol propane, pentaerythritol, diethanolthioether, cyclohexanediol and the likes, as well as aromatic such as hydroquinone, resorcinol, etc.
Examples of such polyols are: poly(oxyethylene)glycol, poly(oxypropylene)glycol,bisphenol-A oxypropylate.
Moreover, amongst such polyols are comprised the saturated polyesterpolyols obtainable by reaction of carboxylic acids such as terephthalic, isophthalic, succinic and adipic acids as well as mixtures thereof with glycols such as: ethyleneglycol, propyleneglycol, bisphenol-A dihydroxyethylether, tetramethyleneglycol or with higher homologues.
A typical polyester polyol usable for the objects of the present invention are products known under the trade name of MULTRATHANE produced by Mobay.
Last, but not least, polyols usable for compositions according to this invention are those based on hydroxy-terminated polycaprolactones, typical examples of which are TONE polyols produced by Union Carbide or CAPA polyols produced by La Porte, and hydroxy-terminated polycarbonates preferentially containing 1,6-hexanediol or 1,4-cyclohexanedimethanol in the polymer chain, examples of which are the commercial products known under the trade name DURACARB produced by PPG Industries.
The polyols deriving from the condensation with alkylene oxides, in particular poly(oxypropylene)glycols, the polyester polyols and the polyetheresterpolyols are amongst the preferred polyols.
For the compositions of this invention it is preferable that the component (B) shall consist of a mixture of a diol with a polyol with a functionality greater than 2; however, and in particular for compositions suited to be used in processes differing from the "Lay-up" process, the diol may be absent, provided that the NCO/OH ratio herein above defined, is preferably within the range of from 4 to 7.
As vinylester resins, constituting component (C), are usable all common vinylester resins in commerce, inclusive of mixtures of neat polymer in a vinyl or divinyl monomer, and having such a viscosity as to confer to the mixture of A+B+C a viscosity comprised between 100 and 400 cPs at 20.degree. C.
More particularly, the polymeric fraction of such vinylester resin may show the following structure: EQU C--I--(D--N).sub.t --D--I--C
wherein:
t=a number comprised between 1 and 5. PA2 tert-butylperbenzoate, PA2 tert-amylperbenzoate, PA2 tert-butylperoxyacetate; PA2 di-n-butyl-diperoxyphtalate, or a combination of said peroxy-compounds in a total quantity of 0.5-3% by weight;
Resins of the above described type and usable for the purpose of the present invention, as well as methods for their preparation, are described in U.S. Pat. Nos. 3,876,726, 4,213,837, 4,182,830 and in European Patent Application No. 48,117.
Other vinylester resins usable for the purpose of the present invention may be those described by the following general structure: EQU A--(--D--M).sub.t --D--A
wherein:
The vinyl and divinyl monomers present in such vinyl ester resins consist of vinyl esters such as: vinyl acetate and the alkyl acrylates and methacrylates (with the alkyl containing from 1 to 20, but preferably from 1 to 10 carbon atoms), such as: methyl acrylate, ethylacrylate, n- and isopropylacrylate, n-, iso- and tert.-butylacrylate, as well as the aryl-, alkaryl-, aralkyl-, cycloalkyl acrylates and the corresponding methacrylates.
Such vinyl monomers may, moreover, consist of aromatic vinyl compounds such as styrene and its alkyl derivatives such as d-methylstyrene and vinyltoluene as well as the vinyl nitriles such as acrylonitrile and its derivatives such as methacrylonitrile.
Divinyl monomers comprise, for instance, alkylen glycoldimethacrylate, divinylbenzene and diallylphthalate.
The unsaturated polyester resins that constitute the component (C) comprise the polyester mixtures with vinyl or divinyl monomers, in which the polymeric fraction (polyester) derives from the esterification of dicarboxylic acids or of their anhydrides with glycols of various nature, and in which at least one fraction of the dicarboxylic acid or of the glycol, or of both, contains unsaturation of the ethylenic type (olefinic).
Examples of such products include resins formed by esterification of maleic, fumaric, itaconic acids or their mixtures, possibly in combination with saturated aromatic or aliphatic dicarboxylic acids, such as phthalic acids and their anhydrides, with ethylene-, propylene-, diethylene-, dipropylene-, glycol and possibly with 1,4-butanediol.
Preferably there are used polyesters derived from the condensation of maleic and/or fumaric and/or isophthalic acids with ethylene glycol or mixtures of glycols.
The vinyl or divinyl monomers present in the unsaturated polyesters which form component (C), are substantially the same which have previously been described for the vinylester resins.
As radical polymerization initiators (component (D)) are mentioned, for exemplifying purposes, the organic peroxides such as the alkyl esters of peroxycarboxylic acids in which the alkyl contains from 1 to 20 carbon atoms, but preferably contains from 1 to 5 carbon atoms, and preferably is: tert-butyl, n-butyl and tert-amyl; cumenehydroperoxide, ethylbenzenehydroperoxide, dicumylperoxide, di-tert-butylperoxide, hydrogen peroxide and, moreover, the azo-compounds such as for instance azo-bis(isobutyronitrile) and 2,2'-azobis(2,4-dimethylvaleronitrile).
Initiators preferred for the purpose are: perbenzoate and peracetate of tert-butyl or tert-amyl and dibutyldiperoxyphthalate.
These initiators are selected for exemplifying purposes and are not intended for limitation.
As initiator decomposition promoters (component(E)) are cited the organic salts of transition metals such as: Mn(II) and Co(II) and the copper salts soluble in resins (C); more particularly acetylacetonates, carboxylates and the alkanoates of said metals and specifically their naphthenates, octanoates, hexanoates and decanoates. Such salts are preferably used in the form of a solution in plasticizers or in fluids which are reactive with at least one of the above described components (A) and (C), such as for instance a glycol, an unsaturated fatty acid or its ester, and the likes.
As decomposition promoters may moreover be cited the aromatic tertiary amines commonly used for this purpose in radical polymerization processes, amongst which there may, for example, be cited the dialkylanilines such as diethylaniline and N-(3-ethylcyclohex-2-enyl)aniline.
Preferred decomposition promoters in the process of this invention are the cobalt salts, as examples of which may be cited the octanoates and neodecanoates, as well as diethylaniline.
As trimerization catalysts component (F)) there may be cited aliphatic tertiary amines and, preferably, aliphatic tertiary polyamines such as: N,N,N',N",N"-pentamethyldiethylenetriamine, N-(2-hydroxyethyl)N,N',N'-trimethylethylenediamine, tetramethylethylenediamine; the aminoalkyltriazines, such as 2,4,6-tris(dimethylaminopropyl) triazine; the carboxylates of quaternary ammonium salts such as, for example, N,N,N-trimethyl-N-(2-hydroxy)propylammonium 2-ethylhexanoate, the carboxylates of metals of groups I and II and of transition metals such as potassium octanoate, potassium 2-ethylhexanoate, lead acetate and lead stearate; the catalysts prepared "in situ" from tertiary amines and epoxy or aziridine derivatives (epoxy resins, phenylglycidylether), and, moreover, aminoalkylphenols such as 2,4,6-tris(dimethylaminomethyl)phenol, 2,6-bis(dimethylaminomethyl)phenol and, 1,3-diazobicyclo(4,5,0)undec-2,3-ene and 1,3-diazobicyclo(3,4,0)non-2-ene and combinations of the above.
Particularly suited for the purpose are the trimerization catalysts containing N,N'-dialkyl derivatives of glycine salts of alkali metals such as, for example sodium N-(2-hydroxy-5-nonylphenyl) methyl-N-methylglycinate whose preparation is described in U.S. Pat. No. 3,896,052. either as such or in admixture with the previously mentioned trimerization catalysts.
The compositions according to this invention show pot life times suitable for application in several processes based on thermosetting resins and can provide, preferably for "lay-up" process, pot lives greater than 30 min. at 25.degree. C.; in addition they are capable to harden essentially completly at room temperature.
Said compositions allow one to obtain thermosetting resins possessing improved impact strength and exhibiting a lower shrinkage rate with respect to the unsaturated vinylester and polyester resins of the Prior Art, without prejudice for the other mechanical properties possessed by said resins, besides higher self-estinguishing properties.
Moreover, said compositions offer the advantage of a low content in styrene and in other volatile products with respect to that of the unsaturated polyesters and vinylesters.
They are suited for the preparation of manufactured articles through methods of the RTM (Resin Transfer Molding) type, and especially for the manufacture of composite materials by means of "lay-up" methods.
For such applications are perticularly suited the compositions having a viscosity at 20.degree. C. comprised between 400 and 3000 cP. Said viscosity values may by attained means of a suitable selection or choice of the type of isocyanate, of polyol and/or of the quantity of vinyl monomer present in the (C) component, according to selection criteria by persons skilled in the Art.
The composition object of the present invention may be used for preparing composite materials by the traditional processes known in the Art such as "lay-up", pultrusion, filament winding, RTM etc., using for this purpose organic or inorganic fibers such as polyamide, aramide, carbon, silicon carbide, glass etc., in the form of continuous fibers or of staples, of fabrics, mats, layers or randomly arranged.
In general, the compositions according to the present invention allow to obtain thermosetting resins having an impact strength (measured without indent) greater than 100 J/m, a bending module of at least 20000 kg/cm.sup.2, deformation at break under bending greater than 2% and a shrinkage rate during cross-linking below 8%, but preferably below 4%.
The HDT values of the resins in general are greater than 80.degree. C., but preferably greater than 100.degree. C.
For the resinous component (C) of the compositions the preferred ones are the vinylester resins.
Some of the preferred compositions according to this invention are those in which the polyol (component (B)) is represented by a polypropyleneglycol and/or by a polyesterpolyol of a molecular weight comprised between 300 and 4000, possessing a functionality comprised between 2 and 4, extremes included, and in which the molar ratio NCO/OH is comprised between 3 and 7.
Further compositions, amongst the preferred ones, are those of the above cited type and in which the isocyanate is represented by a polymeric MDI or by a modified MDI carbodiimide, and shows a functionality between 2 and 3.
The compositions of the present invention may be prepared by a simple and simultaneous admixture of all the components from (A) to (G), as illustrated above.
However, in order to avoid premature cross-linking reactions of the composition, it is advisable to maintain such components suitably separated from each other and to mix them together just at the moment at which it is intended to effect within a short time the cross-linking of the composition and the preparation of the manufactured article. Preferably to above mentioned components are grouped into two batches, the first of which consists of components (B), (C), (E) and (F), while the second consists of components (A) and (D).
The mineral charge or filler (G), if and when used, may be admixed either in the first batch or the second one.
The cross-linking of the composition may be carried out within a temperature range of between 10.degree. and 150.degree. C.
The preferred conditions depend, at any rate, on the type of application.
More particularly, for the preparation of composites with the "lay-up" method, one preferably should carry out the cross-linking at temperatures comprised between about 10.degree. and 60.degree. C., while in the "resin transfer molding (RTM) the temperature may even attain 150.degree. C., with a lower limit of 10.degree. C. Operating under such preferred conditions implies a particular selection of the catalytic cross-linking system.
Preferred catalytic systems are, for instance, those consisting of the following combinations of the compounds, the quantities of which are herein expressed in percent by weight on the whole of the composition.
The components of the above illustrated catalytic systems may be used either as such or, if it is required to facilitate the dispersion in the resin, in the form of a solution in reactive solvents such as, for instance, diols, or in not reactive media such as plasticizers.